1. Field of the Invention
The present invention generally relates to synchronization apparatus and method, and more particularly to correlation interval synchronization apparatus and method for an orthogonal frequency division multiplexing (OFDM) system.
2. Description of the Prior Art
Orthogonal frequency division multiplexing (OFDM) is a communication technique that applies frequency division and multi-carrier modulation, and is widely employed in a variety of digital communication systems, such as the Digital Multimedia Broadcasting (DMB) system or the Digital Audio Broadcasting (DAB) system. The DMB is a digital wireless communication system established on the DAB standard for transmitting multimedia data to a portable device, such as a cellular telephone. In the DMB system, the controllability of time offset of a frame is a critical factor for the efficiency of a receiver. In the conventional system, such as the system disclosed in “PC-based receiver for Eureka-147 digital audio broadcasting,” IEEE Trans. on Broadcasting, vol. 47, No. 2, June 2001, by Jaehee Cho, a power algorithm (1) is used to estimate the time offset:
                    τ        =                                            MAX              n                        ⁢                                          Energy                ⁡                                  [                                                            ⅈ                      ⁢                                                                                          ⁢                                              q                        n                                                              ,                                          ⅈ                      ⁢                                                                                          ⁢                                              q                                                  n                          +                          W                                                                                                      ]                                                            Energy                ⁡                                  [                                                            ⅈ                      ⁢                                                                                          ⁢                                              q                                                  n                          +                          W                                                                                      ,                                          ⅈ                      ⁢                                                                                          ⁢                                              q                                                  n                          +                                                      2                            ⁢                            W                                                                                                                                ]                                                              +          W                                    (        1        )            where W is the operation window, iqi is the i-th output of demodulation (such as I/Q demodulation), and Energy[a,b] denotes the total energy within the interval enclosed by a and b.
The conventional system requires time-consuming operations. Take the algorithm (1) for example, as substantial time is consumed in the division operations, efficient frame synchronization becomes impossible. Accordingly, a need has arisen to propose a synchronization apparatus and method that could simplify the operations, make real-time operation suitable for application specific integrated circuits (ASICs), and improve synchronization accuracy.